The prior art discloses a variety of powdered compositions that produce ClO2 gas under a variety of conditions. Included in these are materials for the controlled sustained release of ClO2 (CSR materials), which release ClO2 when exposed to water vapor. Also included are materials disclosed by which produce ClO2 when exposed to light.
It is desirable for ease of use and disposal for such materials to be contained or packaged in a manner that contains the powder in a porous pouch (i.e., a sachet) or for it to be extruded into a polymer matrix film, such as polyethylene. In this manner the user is protected from direct contact with the powder, and spent powder may be more readily removed from the area that was treated.
Unfortunately, sachets are relatively bulky and expensive to fabricate, and in small sizes are very light and difficult to handle. As a result, the cost of packaging powders in small sachets (less than about 2 grams in size) is often impractically high.
Extruded polymer sheet material can be relatively less expensive to produce in small sizes, because the sheet may be produced in a large economical size, and then smaller size pieces may be inexpensively cut from the larger sheet. However, due to the low decomposition temperature of the chlorite anion that is incorporated into all ClO2 producing materials, the extrusion temperature of ClO2-releasing polymer sheet must be no higher than about 150-160° C. If the temperature is above that, then the amount of chlorite that is lost by decomposition during extrusion can be unacceptably high. This has limited the choice of polymer matrices to those comprising a substantial amount of relatively low melting, low density polyethylene. But polyethylene is an undesirable matrix material because it is not highly permeable to water vapor used to initiate the release of chlorine dioxide from most chlorine dioxide-releasing materials. Plus the extrusion temperature of polyethylene is about 150 degrees C., so it is right on the borderline where decomposition of chlorite anion can occur. Since chlorite decomposition can lead to explosive oxidation of the polyethylene, such extruded sheet materials typically contain lower concentrations of chlorite anion than many powdered versions. Lower chlorite content, in turn, limits their maximum yield of ClO2.